Mohammad Akbari

  Abstract

  A serious threat to cognitive radio networks which sense the spectrum in a cooperative manner is the transmission of false spectrum sensing data by malicious secondary nodes. This enforces the system to acquire authentication. This issue is beyond regular authentication of data origin which assurances that messages are indeed from who they claim they are from. Actually, the decision maker needs to determine the reliability or trustworthiness of the shared data. This thesis utilizes the potential benefits of cooperative spectrum sensing method in a way that it can become applicable when the CR nodes encounter wireless channel uncertainty and some CR nodes that behave maliciously. To this end, after estimating the channel and the PU signal statistics accurately, they are employed to determine the likelihood of CR sensing reports in a MAP hypothesis test scheme for decision about channel occupancy. Also, a computational trust evaluation algorithm is proposed to determine the trustworthiness of each CR user's data and eliminate the effect of SSDF attackers.

  Defense against Primary User Emulation Attacker (PUEA) is the second issue that is considered in this thesis. To this end, an adaptive transmission technique for frequency-hop packet transmission is proposed and its performance is evaluated for certain channels with unknown attacker’s signal parameters. The power in the transmitted signal and the rate of the error-control code are adapted in a way that provides an energy-efficient communications. The performance of the adaptive transmission system is evaluated for channels with some PUE attackers that occupy some fraction of the spectrum band with time-varying partial-band interference and propagation loss.

  Date of Defense: Saturday, February 26, 2011 Time: 3.0 pm

  Place: Class 303, Electrical Engineering Department